1. Field of the Invention
The invention relates to the new surfactants and detergent compositions containing these new surfactants in combination with oxidizing agents.
2. The Prior Art
Certain types of cleaning compositions, such as automatic dishwashing detergents, demand the presence of oxidizing agents to operate effectively. Hypochlorite generating compounds are most commonly employed as the oxidizing agent. Although less economical, peroxygen compounds such as sodium perborate have also been reported as useful.
While the present invention has application beyond automatic dishwashing detergent compositions, it is these type compositions which are of particular commercial concern. Therefore, it is appropriate that the problems associated with automatic dishwashing be here set forth.
Automatic dishwashing detergent compositions employ alkaline salts such as sodium silicate, sodium carbonate and sodium tripolyphosphate as the main cleaning agents. A hypochlorite source is included in the formulation mainly for the purpose of breaking up protein soil. Once solubilized, protein soil, derived from foods such as eggs and milk products, gives rise to foaming problems. Foam generation, in turn, interferes with the cleaning action of the machine dishwasher. Without effective foam suppression, the mechanical cleaning action of the dishwasher is reduced because foam build-up partially insulates tableware from the full force of the aqueous washing composition.
Small amounts of nonionic surfactants are usually added to dishwashing compositions to combat the foam problem. Glassware appearance is, to an extent, also improved by the presence of the surfactant. Indeed, spotting and filming is particularly sensitive criterion by which consumers judge product performance. There is a need for improved performance on glassware.
Numerous types of nonionic surfactants useful in automatic dishwasher detergent compositions have been reported in the literature. For example, U.S. Pat. No. 3,956,401 (Scardera et al.) reports a C.sub.7 -C.sub.10 alcohol alkoxylated to form a three block grouping of oxypropylene/oxyethylene/oxypropylene. U.S. Pat. No. 4,410,447 (Decker et al.) reports a low foaming surfactant using a C.sub.7 -C.sub.11 primary alcohol as a hydrophobe onto which is first attached oxypropylene units followed by a random oxyethylene/oxypropylene mixture. Not only alkyl but also aromatic hydrophobes have been reported. U.S. Pat. No. 4,436,642 (Scott) discloses use of a C.sub.6 -C.sub.12 alkyl substituted phenol alkoxylated first with a block of propylene oxide and then ethylene oxide. Another structural variation has been the incorporation of an end-capping unit to the alkoxylated chain. European patent application No. 0 197 434 (Pruhs et al.) describes defoaming nonionic surfactants formed from the ethoxylation of C.sub.8 -C.sub.18 alcohol end-capped with C.sub.1 -C.sub.4 alkanol, particularly n-butanol.
Most of the aforementioned defoaming surfactants have been formulated for use in powdered automatic dishwashing detergent formulations. More recently, there has been significant consumer interest in pourable liquid versions. Greater challenges are presented by liquid formulations. With powders, many techniques are available to separate surfactant from the oxidizing agent. Providing a coating over the oxidizing materials is, for instance, one method of protecting surfactant against degradation. Even without special separation techniques, powders by their very nature diminish the interaction between components. On the other hand, liquid formulations require their constituents, including any defoaming surfactants to be more oxidatively stable than would ordinarily be necessary in a powder.
Accordingly, it is an object of the present invention to provide novel nonionic surfactants which are highly efficient defoamers.
Another object of the present invention is to provide novel nonionic surfactants which display improved oxidative stability.
A further object of the present invention is to identify novel nonionic surfactants that not only defoam but have improved effectiveness against spotting and filming problems associated with the cleaning of glassware.
Another object of this invention is to provide an automatic dishwashing detergent composition utilizing the novel nonionic surfactants.
A more particular object of the present invention is to provide a defoaming nonionic surfactant whose oxidative stability is sufficient for incorporation into liquid formulations containing hypochlorite generating oxidizing agents.